1. Venus Astronomy 311 Professor Lee Carkner Lecture 11

2. Venus -- The Goddess of Beauty  Venus is one of the brightest planets in the sky  

3. Venus from Earth  Venus is only seen near the Sun   Venus shows phases  Venus is covered with clouds 

4. Venus Facts  Size: 95% Earth   Orbit: 0.7 AU   Description:

5. Venus’s Retrograde Rotation  When viewed from above the north pole of the Earth, most of the planets:    Venus rotates clockwise   Why is Venus upside down?   We have no evidence of this, however

6. Retrograde Rotation

7. Rotation Rate  Venus rotates on its axis with a period of 243 days   Day is longer than a year  Reason is unclear  

8. Venus from Pioneer

9. Venus’s Atmosphere  In the 1960’s and 1970’s probes were dropped into Venus’s atmosphere  Composition:     Pressure:  Temperature: 750 K (hottest planet in solar system)

10. Chemicals in Atmosphere  A lot of sulfur in atmosphere   Sulfuric acid has vapor point such that it boils on the surface but condenses in the atmosphere to form clouds   Also, hydrofluoric acid (HF), hydrochloric acid (HCl) and other corrosive compounds

11. Structure of Atmosphere  68 km and up --  48-68 km –  30-40 km –  0-30 km –  Temperature:  Pressure:   90 atmospheres at surface

12. Temperature in Atmosphere

13. Formation of Atmosphere 1) Early Venus heats up, water evaporates 2) 3) Ultraviolet light disassociates water and destroys it 4) 5) 6) Volcanoes outgas sulfur, forms sulfuric acid clouds

14. Venera 13 Mock-up

15. Venera 13 on Venus

16. The Surface of Venus     Chemical analysis indicates that surface rocks are similar to basalt, a volcanic rock

17. Interlude Planetary Configurations

18. Magellan Maps Venus  Venus’s atmosphere is so thick that you cannot see the surface from orbit   Our map of Venus comes from the Magellan spacecraft (1990) 

19. Radar Map of Venus

20. Global Surface of Venus  Surface is generally level (smoothed by lava)   Many volcanoes and lava features  The entire surface is the same age   Surface features named after women

21. Gula Mons

22. Vires-Akka Chasma

23. Alcott Crater

24. A Corona

25. Lava Domes

26. The Highlands of Aphrodite Terra

27. Danu Mountains

28. Wind Blown Streak

29. Sif Mons

30. Volcanism on Venus  Evidence for Volcanism:  smoothed surface   lava channels   visible shield features

31. The Interior of Venus   No plate tectonics   moving lava disturbs the crust enough to produce a few mountains and highlands   too hot or too dry?   Venus probably has a molten core 

32. Summary  Earth-Sized, hot, thick atmosphere  (Earth’s evil twin)  Rotates slowly and upside-down  Studied by Venera landers and Magellan radar mapper

33. Summary: Atmosphere  Composed of CO 2 with sulfuric acid clouds  Thick (90 atmospheres) :  No water to wash out CO 2  Hot (750 K):  Powerful greenhouse effect

34. Summary: Surface  Volcanism shapes surface and outgases sulfur  See volcanoes and lava flow channels  Surface mostly flat with a few highlands  Nature of core is unknown